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Discovering an interior leak is dismaying, but just because your house is on a slab, it doesn’t automatically indicate a foundation problem. While the leak could be associated with a cracked slab, if it’s around a wall, the chances are good the water is coming from somewhere else. The key is to find the source of the leak quickly so you can make your own repairs or contact the right professional for the job.

Water Supply

The first place to check for a leak is in the water supply system. Turn off all faucets and appliances that use water, such as the dishwasher and clothes washer, and then pull the cover off the water meter to see if the dial is moving. It’s a good idea to leave the cover off for an hour or two. If the dial moves, the leak is in the water supply system and it could be a pinhole leak, a loose fitting, a broken line or a damaged valve. In most slab homes, the main waterline enters the home, and individual supply lines run through the walls to each fixture. If the leak is around a utility room wall, a quick check for water in the utility room tells you if the problem is with the waterline beneath the floor. If the leak is in a different area of the home, some drywall removal is in order to pinpoint the exact spot.

Leaking From Above

Water has a sneaky way of trickling down -- sometimes quite a distance from the point where it enters the home. If you’ve ruled out the water supply system, the next suspect should be the roof. Harsh UV rays can make rubber vent “boots” brittle after a few years, resulting in cracks that let rain seep into the home. Other suspect spots include rusted flashing and missing shingles. Water that enters the roof can follow rafters and then wall studs to the floor before seeping out around a wall. If you discovered the leak after a recent rain, check the attic to see if you find damp rafters, joists or insulation, which would indicate the water is coming from the roof.

Interior Drains

If the leak worsens after use of a specific fixture such as a sink or dishwasher, it could be a problem with that fixture’s drain. Check under sinks first, but if a drainpipe is leaking from a connection in a wall, you have to remove some drywall to find it. Leaks in tub and shower drains are more difficult to reach and repair, but it’s standard practice to “block out” an open section around the drain when pouring the slab. If you have to remove a tub or shower, the trap that lies beneath still is accessible.

Ground Water

Heavy rains and pooling water around the exterior of the slab can cause leakage between the slab and the structural framing of the home. Some building codes require at least 6 inches of exposed slab foundation above the soil. The yard should slope down and away from the foundation to encourage rain to run away from the house.

Slab Problems

No homeowner wants to find a leak originating from a drain cemented in the foundation slab. If the slab shifted from earthquake activity or soil movement, there is a chance it cracked a main drain. If the leaking water has a foul smell, it could be coming from a sewer drain. Repairing this type of leak requires a plumbing contractor who specializes in slab leak detection and repair. Detection might involve the use of a camera or infrared technology. The contractor might make repairs by tunneling under the slab, but breaking out a portion of the slab might be necessary.

About the Author

Glenda Taylor is a contractor and a full-time writer specializing in construction writing. She also enjoys writing business and finance, food and drink and pet-related articles. Her education includes marketing and a bachelor's degree in journalism from the University of Kansas.

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Taylor, Glenda. "Leak Around the Wall on a Slab." Home Guides | SF Gate, http://homeguides.sfgate.com/leak-around-wall-slab-105466.html. 23 February 2015.

Taylor, Glenda. (2015, February 23). Leak Around the Wall on a Slab. Home Guides | SF Gate. Retrieved from http://homeguides.sfgate.com/leak-around-wall-slab-105466.html

Taylor, Glenda. "Leak Around the Wall on a Slab" last modified February 23, 2015. http://homeguides.sfgate.com/leak-around-wall-slab-105466.html

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